Imine complexes of certain transition metals such as iron, palladium, cobalt, nickel and others are important parts of catalyst systems for the polymerization of olefins, see for instance U.S. Pat. No. 5,714,556, World Patent Applications 96/23010, 97/48737, 97/48735, 97/38024, and U.S. patent application Ser. No. 08/991372, filed Dec. 16, 1997 (now U.S. Pat. No. 5,955,555) all of which are hereby included by reference. These and other references generally describe the synthesis of these types of imine complexes as the reaction of the imine containing ligand with various types of transition metal compounds to form the transition metal imine complex. These methods usually involve the use of substantially anhydrous conditions to avoid hydrolysis of the starting transition metal compound and/or any intermediates or the desired final complex.
For the most part, the imines themselves are not commercially available, usually being made from the corresponding carbonyl compound, such as a ketone or aldehyde, and an amine, often an aromatic amine. When made by this method, water is a by-product. Since this imine forming reaction is usually considered to be an equilibrium, to drive the reaction to completion the water is often removed during the synthesis of the imine, for example by distillation, preferably azeotropic distillation, or by formation of a hydrate, preferably an inorganic hydrate.
Thus imine complexes of transition metals are often made in two step processes, imine synthesis, and then synthesis of the metal complex. A simpler, especially one step, synthesis would be preferable if they used the same starting materials since they would usually be cheaper than a two step synthesis.
Many complexes of imines and transition metals have been synthesized and reported in the literature. In addition to the above references, see for instance: H. tom Dieck et al., Inorg. Chim. Acta, vol. 177, p. 191-197 (1990); R. van Asselt, et al., J. Am. Chem. Soc., vol. 116, p. 977-985 (1994); H. tom Dieck, et al., Z. Naturforsch. B, vol. 33, p. 1381 et seq. (1978); H. G. von Schnering, et al., Chem. Ber., vol. 109, p. 1665 et seq. (1976); and H. tom Dieck et al., Chem. Ber., vol. 109, p. 1657 et seq. (1976).
R. van Asselt, et al., Recl. Trav. Chim. Pays-Bas., vol. 113, p. 88-98 (1994) describes the synthesis of certain zinc and nickel (x-diimine complexes from the diketone and aromatic amine. In many of the syntheses, (glacial) acetic acid is present.